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Transcript
GENERATOR SET MOTOR STARTING MOTOR STARTING The following must be taken into account when motors are started while the load is on the generator set: • Type of motor • Method of starting • Starting current requirement • Voltage dip limitations • Sequence in which the motors are started FORMULA The generator set power is calculated as follows: kW gen Where: ∩ motor Created by J. M. J. Lloyd = 0.746 x motor h.p. (output) ∩ motor = motor kW (output) ∩ motor = motor efficiency Uncontrolled once printed DIRECT ON LINE (D.O.L.) STARTING In D.O.L. starting the motor is started with the windings connected in DELTA so full voltage is applied directly to the motor terminals on start-up and during running. MOTOR STARTING CURRENT A delta connected motors’ starting current is 6 times its full load current. ALTERNATOR OVERLOAD CAPACITY The generator set alternators’ overload capacity is 2.5 times its rated output. FORMULA The ratio of generator set kW to motor kW is calculated as follows: Created by J. M. J. Lloyd kW gen x 2.5 = 6 x motor kWm ∩m kW gen = 6 x motor kWm 2.5 x 0.9 kW gen = 2.67 times motor KWm Uncontrolled once printed STAR DELTA STARTING In Star Delta starting the motor is started with the windings connected in Star so the starting voltage is reduced by √3. MOTOR STARTING CURRENT AND TORQUE The starting current is reduced to 2 times its full load current The starting torque is reduced to 1/3 of the D.O.L. value FORMULA The ratio of generator set kW to motor kW is calculated as follows: Created by J. M. J. Lloyd kW gen = 2 x motor kWm 2.5 x 0.9 kW gen = 0.9 times motor kWm Uncontrolled once printed